[PATCH v7 1/5] random: Blocking API for accessing nonblocking_pool

[Stephan Mueller <smueller@chronox.de>]

The added API calls provide a synchronous function call
get_blocking_random_bytes where the caller is blocked until
the nonblocking_pool is initialized.

CC: Andreas Steffen <andreas.steffen@strongswan.org>
CC: Theodore Ts'o <tytso@mit.edu>
CC: Sandy Harris <sandyinchina@gmail.com>
Signed-off-by: Stephan Mueller <smueller@chronox.de>
---
 drivers/char/random.c  | 18 ++++++++++++++++++
 include/linux/random.h |  1 +
 2 files changed, 19 insertions(+)

diff --git a/drivers/char/random.c b/drivers/char/random.c
index 9cd6968..3d1c027 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -1245,6 +1245,24 @@ void get_random_bytes(void *buf, int nbytes)
 EXPORT_SYMBOL(get_random_bytes);
 
 /*
+ * Equivalent function to get_random_bytes with the difference that this
+ * function blocks the request until the nonblocking_pool is initialized.
+ */
+void get_blocking_random_bytes(void *buf, int nbytes)
+{
+	int rc;
+
+	if (unlikely(nonblocking_pool.initialized == 0)) {
+		do {
+			rc = wait_event_interruptible(urandom_init_wait,
+						nonblocking_pool.initialized);
+		} while (rc == -ERESTARTSYS);
+	}
+	extract_entropy(&nonblocking_pool, buf, nbytes, 0, 0);
+}
+EXPORT_SYMBOL(get_blocking_random_bytes);
+
+/*
  * This function will use the architecture-specific hardware random
  * number generator if it is available.  The arch-specific hw RNG will
  * almost certainly be faster than what we can do in software, but it
diff --git a/include/linux/random.h b/include/linux/random.h
index b05856e..796267d 100644
--- a/include/linux/random.h
+++ b/include/linux/random.h
@@ -14,6 +14,7 @@ extern void add_input_randomness(unsigned int type, unsigned int code,
 extern void add_interrupt_randomness(int irq, int irq_flags);
 
 extern void get_random_bytes(void *buf, int nbytes);
+extern void get_blocking_random_bytes(void *buf, int nbytes);
 extern void get_random_bytes_arch(void *buf, int nbytes);
 void generate_random_uuid(unsigned char uuid_out[16]);
 extern int random_int_secret_init(void);
-- 
2.1.0